use repr() instead of backticks

mercurial/changelog.py

@@ -179,7 +179,7 b' class changelog(revlog):'
 
         user = user.strip()
         if "\n" in user:
-            raise RevlogError(_("username %s contains a newline") % `user`)
+            raise RevlogError(_("username %s contains a newline") % repr(user))
         user, desc = util.fromlocal(user), util.fromlocal(desc)
 
         if date:

mercurial/ui.py

@@ -350,7 +350,7 b' class ui(object):'
         if not user:
             raise util.Abort(_("Please specify a username."))
         if "\n" in user:
-            raise util.Abort(_("username %s contains a newline\n") % `user`)
+            raise util.Abort(_("username %s contains a newline\n") % repr(user))
         return user
 
     def shortuser(self, user):